Abstract:
By using the precipitation data from 132 meteorological stations in Sichuan, and the daily outgoing long-wave radiation (OLR) data from NOAA, the prominent differences of low frequency convection propagates in abnormal tropic East Indian Ocean MJO years during the main rainy season, the physical processes which impact the precipitation in the Sichuan Basin during the main rainy season have been analyzed. This research study discusses the propagation path and source of the low frequency oscillation of the tropical East Indian Ocean MJO in the active years towards the Sichuan Basin, as well as the respective impact of low frequency oscillation of the southwest monsoon systems in the Bay of Bengal and the East Asian subtropical monsoon systems on the low frequency convection activities of the Sichuan Basin during the main rainy season. Research shows that: the low frequency convection in the tropical Indian Ocean stimulates the active convection of the southwest monsoon ISO in the Bay of Bengal, and propagates towards the Sichuan Basin under the influence of a southwest air flow. the low frequency convection initially propagates from the east of tropical Indian Ocean towards the tropical ocean south of the Philippine Islands, then propagates northward to the eastern Asian subtropical region, stipulates the strengthened activity of East Asian subtropical monsoon ISO, and then propagates westward toward the Sichuan Basin. The results suggest the abnormal activities of tropical Indian Ocean MJO impose the precipitation of Sichuan basin by the co-action of two monsoon systems, Southwest Monsoon of Bay of Bengal and East Asian subtropical summer monsoon. These two monsoon systems impose the abnormal conversion in flood season of Sichuan basin, thereby the precipitation of flood season is imposed as well.